I don't understand why should we work hard to get all (or half, but that's still billions) people in the world to do this if we can simply write it into the lic

I don't understand why should we work hard to get all (or half, but that's still billions) people in the world to do this if we can simply write it into the license terms and use the already existing legal framework made exactly for this purpose. I also don't understand the claimed inflexibility, IP rights are one of the most flexible pieces of legislation I know, and your license can be as flexible as you wish too. On the other hand, what in the hell is flexible about laws made only for this purpose?